This invention relates generally to a cleaning apparatus, and more particularly concerns preventing toner emissions and flat spots on a retracting cleaning brush.
In an electrophotographic application such as xerography, a charge retentive surface (i.e., photoconductor, photoreceptor or imaging surface) is electrostatically charged, and exposed to a light pattern of an original image to be reproduced to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on that surface form an electrostatic charge pattern (an electrostatic latent image) conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate (e.g., paper), and the image affixed thereto to form a permanent record of the image to be reproduced. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is well known, and useful for light lens copying from an original, and printing applications from electronically generated or stored originals, where a charge surface may be imagewise discharged in a variety of ways. Ion projection devices where a charge is imagewise deposited on a charge retentive substrate operates similarly.
Although a preponderance of the toner forming the image is transferred to the paper during transfer, some toner invariably remains on the charge retentive surface, it being held thereto by relatively high electrostatic and/or mechanical forces. Additionally, paper fibers, Kaolin and other debris have a tendency to be attracted to the charge retentive surface. It is essential for optimum operation that the toner remaining on the surface be cleaned thoroughly therefrom.
A commercially successful mode of cleaning employed on automatic xerographic devices utilizes a-brush with soft electrically biased conductive fiber bristles or with insulative soft bristles which have suitable triboelectric characteristics. The brush fibers retain particles removed from the surface. A detoning roll is one common method of removing these particles from the cleaning brush fibers.
When an electrostatic brush, detoning roll cleaner is in standby and the brush is stationary, the brush after time will take a set in the nip region between the brush and any contacting surface. The brush fibers will deform in such a way as to cause a flat spot in the brush. This flat spot impairs cleaning and impacts photoreceptor motion quality.
The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
U.S. Pat. No. 5,260,754 to Yano et al. discloses a cleaning device incorporated in an image forming apparatus for removing a toner remaining on a photoconductive drum by a fur brush and collecting the removed toner by a collecting roller. The cleaning device selectively moves the fur brush into and out of contact with both of the photoconductive drum and collecting roller.
U.S. Pat. No. 5,177,553 to Ohike et al. discloses a method of controlling rotation of a brush in a cleaning device of an image forming system. In the method, the brush is raced together with the photoreceptor which is in contact with the brush for a predetermined time in a warming-up period before the image forming operation starts, in an image-forming rest period, or when a new cartridge constituted by the photoreceptor and the cleaning device is set into the image forming system, so that the fibers of the brush which have been transformed during the rest of rotation are recovered into their original shapes.